1. Field of the Invention
The invention concerns a projectile which is to be fired mortar-like from a barrel and which is provided with a control surface assembly comprising control surface vanes which can be pivoted out from a sub-calibre launch position into an over-calibre functional position and which can involve gliding planes or in particular tail control rudders or stabilisation fins.
2. Discussion of the Prior Art
When a projectile with an over-calibre control surface assembly is fired from a barrel the pivotal deployment procedure in respect of the fins which are pivotably mounted for example at the tail of the projectile may be initiated only after leaving the barrel. Unlocking devices which are especially adapted to the respective design configuration involved are known for that purpose. For example DE 34 32 614 A1 describes a projectile with an inflatable body which is folded in when in the rest condition and which, for pivoting open wings of the projectile, is subjected to the action of a highly stressed gas from a pressure container which is specifically carried by the projectile for that purpose, whereby it expands in the radial direction and thus applies a force to the folded-in wings.
DE 35 07 677 A1 discloses a projectile with a control surface assembly in the form of rudder blades which are held mounted pivotably to the tail structure transversely with respect to the longitudinal axis of the projectile, wherein, until being fired from the barrel, the arrangement ensures that the rudder blades are held in a position which is true to the calibre involved and which can be then definedly released upon launch. For that purpose, that arrangement has positively locking arresting means using displaceable securing pins between each rudder blade end face and the peripheral surface of the tail structure. Due to the launch acceleration, each securing pin is displaced in opposite relationship to its holding configuration, whereby the outward pivotal movement of the respective rudder blade into its over-calibre functional position is then enabled.
A similar projectile with an over-calibre control surface assembly whose rudder blades are folded into the projectile structure for storage, transportation and launch and are arrested at their ends in that position until they are released by a securing device, in dependence on launch acceleration, for their outward pivotal movement, is known from DE 37 21 512 C2. In order to embody a compact and functionally efficient securing device which releases all rudder blades at the same timexe2x80x94but not too early xe2x80x94for deployment, the arrangement has a plunger member which engages simultaneously into all rudder blades and which is displaceable axially with respect thereto in the launch direction and which is moved into its release position simultaneously for all rudder blades only upon a reduction in the projectile launch acceleration.
As a consequence of their securing devices which are to be specifically designed for the control surface assembly which is precisely involved in each case, all those known projectiles are of a configuration which is really complicated and expensive in terms of structure and apparatus. To avoid such complication and expenditure it is also known, in the case of projectiles which are fired spin-free and therefore from a smooth barrel, that is to say a barrel which does not have any rifling, for the control surfaces which can be extended at the tail of the projectile to be caused to bear simply against the smooth internal peripheral surface of the barrel, upon being launched from the barrel. That gives rise to problems in particular when the situation does not involve conventionally radially extensible rudder blades (referred to as fins) or wings, but so-called wrap around tail assemblies. In such assemblies shell-shaped control surfaces, in the manner of hollow-cylinder portions, bear in their launch position of being equal to the calibre, against the peripheral surface of the projectile at the outside and against the launch barrel at the inside. Upon the mechanical release thereof as a result of leaving the barrel they pivot outwardly about axes in parallel relationship with the longitudinal axis of the projectile.
If however a projectile is to be spin-stabilised and therefore is to be fired from a barrel provided with rifling, then, when passing through the barrel, due to the extreme acceleration forces which occur in the barrel, damage due to the rifling cutting into the control surfaces sliding therealong cannot be avoided. Then, in free flight, that can have a crucially detrimental effect on the functional efficiency of the projectile, for example because of worsened directional stability.
In consideration of those aspects, the object of the present invention is to provide a projectile, in particular a projectile which is to be launched in the manner of a spin-stabilised mortar projectile, in which control surfaces which are provided at the tail and which are pivotable about axes parallel or transversely with respect to the longitudinal direction of the projectile are reliably and securely fixed in their calibre-true storage position by means of simple structural measures and, after leaving the barrel, are equally reliably released for deployment into their over-calibre functional position.
In accordance with the invention that object is attained in that a securing pot having a pot peripheral portion and a pot bottom is temporarily fixed to the tail in such a way that the vanes are held in their launch position by the pot peripheral portion, and that a pressure chamber is present between the tail end face of the projectile and the pot bottom of the securing pot, wherein the pot bottom has at least one propellent gas inlet which opens into the pressure chamber.
The projectile which in accordance with the invention is provided with a securing cup or pot for holding control surfaces in the sub-calibre position has the advantage that, in its interior, the securing cup or pot which is equal to the barrel calibre, reliably and securely holds the vanes provided at the tail of the projectile in the inwardly folded storage position. In that way the securing pot also has an optimum protective function in terms of handling requirements in a magazine. That protective function relates not only to the above-mentioned control surfaces but also further ballistic and sensor structures of the projectile, which are disposed at the tail end towards the propellent charge gas chamber in the barrel. A further quite considerable advantage of the projectile which is equipped in accordance with the invention is that the securing pot is reliably jettisoned from the projectile without the use of outside energy after the projectile issues from the barrel, in order thereby to enable deployment of the rudders or the like control surfaces. That is achieved by means of the increased pressure of the propellent gases which, for launching the projectile from the barrel, are produced therein from burning propellent means behind the projectile. That pressure can temporarily amount to the order of magnitude of up to 100 bars and even more. It also passes into the interior of the pot behind the tail of the projectile, through a bottom end opening. After leaving the barrel, that high internal pressure in the pot is suddenly only still subjected to the atmospheric pressure so that the securing pot is rapidly and reliably pushed off the tail of the projectile by the increased internal pressure and thereby liberates the vanes or the like control surface assembly for outward pivotal movement into the over-calibre functional position thereof. That outward pivotal movement is effected under the action of the centrifugal forces of the projectile which is fired with spin and can be still more promoted in known manner by suitable drive systems such as spring elements, pyrotechnic force elements or the like.
In order reliably to guarantee the high pressure in the pressure chamber between the tail of the projectile and the bottom of the securing pot which is fitted thereover during firing of the projectile from the barrel which involves a smooth or preferably a rifled barrel, it is desirable if the pot wall is pressure-tightly sealed in relation to the tail of the projectile. For that purpose, it is possible to provide behind the control surface assembly at least one sealing ring for pressure-tightly sealing off the pot wall at the inside relative to the tail of the projectile. It is helpful for the same purpose if the tail of the projectile also has, in front of the control surface assembly, at least one sealing ring for pressure-tightly sealing it off with respect to the wall of the securing pot. For definedly establishing the pressure chamber between the tail end face and the bottom of the securing pot, the tail end face can be provided with an annular contact face and the securing pot bottom can be provided with an annular support face which bear against each other.
The peripheral portion of the pot can be temporarily fixed to the tail of the projectile by means of shearing pins. The shearing pins afford both a safeguard in terms of transportation and also an in-barrel safeguard. The shearing pins are dimensioned in such a way, that is to say they are formed with desired-rupture locations, that reliable separation of the securing pot from the tail of the projectile is implemented as a consequence of the high pressure in the pressure chamber between the tail end face of the projectile and the bottom of the securing pot, relative to the atmospheric pressure of the outside ambient atmosphere, as occurs after the projectile issues from the barrel. Those pins however cannot be sufficiently loaded to also transmit the twist to the projectile, which is exerted on the wall of the securing pot by the rifling, as the projectile passes through the barrel. Therefore, arranged between the tail of the projectile and the bottom of the securing pot there is also at least one key which prevents relative rotational movement but which comes axially out of engagement when the pot is jettisoned. In order to be able to reliably accommodate that engagement and the high pressure in the pressure chamber during the acceleration of the projectile in the barrel, it is desirable if the bottom of the securing pot involves a large thickness of material, in comparison with the wall of the pot.
The propellent gas inlet into the pot interior is desirably provided with a directional function and is therefore in the form of a nozzle. The nozzle can have a male screwthread portion with which it is screwed into a screwthreaded through hole provided in the bottom of the securing pot. The nozzle can have a central longitudinal hole connected to transverse holes. Such a design configuration ensures that a suitably high pressure is built up during launch of the projectile in the pressure chamber due to the propellent charge gases. The pressure chamber in the pot is therefore virtually pumped up in the barrel with the propellent charge gases, to a suitably high pressure. Under pressure, the large-size tail end face of the projectile and the correspondingly large-size bottom of the securing pot result in a correspondingly high pressure which is directed axially against the bottom of the securing pot and with which the securing pot is separated from the tail of the projectile, with the securing pins being sheared off, after the projectile issues from the barrel, as a result of the above-mentioned pressure difference, so that for example the control surfaces which are pivotably mounted to the tail of the projectile can be pivoted out into their over-calibre position for flight of the projectile.
The projectile according to the invention which is to be fired from a barrel is thus of a very simple structure in terms of ensuring that its tail control surface assembly is in a position which is still sub-calibre when starting, in which respect the securing pot not only has a protective function for the control surface assembly which is still to be held in the inwardly folded condition and for ballistic and sensor structures at the tail end of the projectile, but it also guarantees reliable release of the control surface assembly by virtue of being jettisoned from the tail of the projectile.